Surges in electronic circuits are caused by internal conditions — switching operations from other electronic components or due to external conditions on the AC power mains — switching operations in the power grid or from nearby lightning strikes, either directly to the power distribution system or to nearby ground. Electronic products have to be surge immune to ensure their continued reliable operation if subjected to realistic levels of surge voltages, and they are required to comply with safety requirements.
The VR series is a perfect fit when an anti-surge resistor is required. Other major applications of VR resistors are: AC mains protection, isolation between primary/secondary circuits in TVs, voltage dividers, ignition/switching circuit in electronic ballasts. They are offered in three different power ratings: VR25 ¼ Watt, VR37 ½ Watt, and VR68 1 Watt. The VR series uses metal glaze technology and is offered in resistance values from 100K to 68Mohms (higher values available upon request) and can handle up to 10KVolts (VR68). Series resistance range power rating Tol (%) Max. Permissible Voltage VR25 100K-22M ¼ Watt 5% and 1% 1.6 KV (DC) VR37 100K-33M ½ Watt 5% and 1% 3.5 KV (DC) VR68 100K-68M 1 Watt 5% and 1% 10KV (DC). The VR37 and VR68 meet the safety requirements of UL1676 (from 510Kohms to, BS 60065, VDE 0860 and CQC.